限流与熔断降级

通过@SentinelResource来指定出现限流和降级时候的异常处理策略。

pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>sentinelresource</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>sentinelresource</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-sentinel</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.SR1</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-alibaba-dependencies</artifactId>
                <version>0.2.2.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

application.properties

spring.application.name=sentinel-sentinelresource
server.port=8087
spring.cloud.sentinel.transport.dashboard=http://10.17.12.158:8084

启动类

package com.example.sentinelresource;

import com.alibaba.csp.sentinel.annotation.aspectj.SentinelResourceAspect;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

@SpringBootApplication
public class SentinelresourceApplication {

    public static void main(String[] args) {
        SpringApplication.run(SentinelresourceApplication.class, args);
    }

    @Bean
    public SentinelResourceAspect sentinelResourceAspect() {
        return new SentinelResourceAspect();
    }
}

业务逻辑

package com.example.sentinelresource.service;

import com.alibaba.csp.sentinel.annotation.SentinelResource;
import com.alibaba.csp.sentinel.slots.block.BlockException;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;

@Service
public class SentinelService {

    protected Logger logger = LoggerFactory.getLogger(getClass());

    // 限流与阻塞处理
    @SentinelResource(value = "doSomeThing", blockHandler = "exceptionHandler")
    public void doSomeThing(String str) {
        logger.info(str);
    }
    //实现限流的异常处理
    public void exceptionHandler(String str, BlockException ex) {
        logger.error("blockHandler:" + str, ex);
    }

    // 熔断与降级处理
    @SentinelResource(value = "doSomeThing2", fallback = "fallbackHandler")
    public void doSomeThing2(String str) {
        logger.info(str);
        throw new RuntimeException("发生异常");
    }
    public void fallbackHandler(String str) {
        logger.error("fallbackHandler:" + str);
    }
}

控制器

package com.example.sentinelresource.controller;

import com.example.sentinelresource.service.SentinelService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.Date;
@RestController
public class HelloController {
    @Autowired
    private SentinelService sentinelService;

    @GetMapping("/hi")
    public String hi() {
        sentinelService.doSomeThing("hi," + new Date());
        return "hi,somebody";
    }

    @GetMapping("/hello")
    public String hello() {
        sentinelService.doSomeThing2("hello " + new Date());
        return "Hello,World!";
    }
}

测试限流

多次请求后

测试熔断降级

发送一次localhost:8087/hello请求(控制台将输出异常信息),比如

curl localhost:8087/hello

在Sentinel-Dashboard上可以看到名为doSomeThing2的资源点,然后点击”降级“按钮,为该资源设置降级规则。 这里选择异常数为3,时间窗口为3秒

验证熔断降级: 每请求一次localhost:8087/hello请求,控制台均将输出异常信息; 当访问次数超过3次后,将调用将直接出发熔断降级。

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